1. Field of the Invention
The present invention relates to a negative resist material formulated with, as a base resin, a high polymer that can be obtained by copolymerizing an indene that may have a substituent or another monomer showing solubility in alkaline or having a structure that can be converted into a functional group that shows solubility in alkaline by a deprotection reaction or the like, and deprotecting the resulting copolymer, which shows high contrast for dissolution rates before and after the exposure, high sensitivity, high resolution and superior etching resistance and is suitable as, in particular, a material for forming a micro pattern or mask pattern for the production of VLSI.
2. Related Art
In recent years, with use of higher integration degree and higher processing speed of LSI, finer pattern rules are being desired. Under such a situation, far ultraviolet ray lithography is considered promising as a fine processing technique of the next generation. The far ultraviolet ray lithography enables processing for even a line width of 0.5 μm or less, and it enables formation of a pattern having side walls approximately perpendicular to a substrate if a resist material showing a low light absorption is used.
The recently developed positive resist materials of chemical amplification type (refer to Japanese Patent Publication (Kokoku) No. 2-27660, Japanese Patent Laid-open Publication (Kokai) No. 63-27829 etc.) utilize a high luminance KrF excimer laser as a light source of far ultraviolet ray and have been developed as promising resist materials for the far ultraviolet ray lithography having superior characteristics such as high sensitivity, high resolution and high dry etching resistance.
However, in the electron ray lithography, which is currently noted as a processing technique for a line width of 0.1 μm or less, a negative resist material of chemical amplification type showing superior pattern size characteristics and so forth and containing a crosslinking agent attracts attentions and has become indispensable also as a mask pattern formation material. As for base resins of these resist materials, negative resist materials using a copolymer of hydroxystyrene and styrene or alkoxystyrene have been reported.
However, resist materials using such base resins as mentioned above have problems without exception. For example, the pattern shape is likely to become a bridge-like shape, a resin having a bulky group in an alkoxystyrene side chain shows lower heat resistance as well as insufficient sensitivity and resolution, and so forth.
In addition, as a problem in the production, while the base resins of these resist materials desirably have a weight average molecular weight of 7,000 or less, polymerization at an extremely low concentration is required for the currently available resists material, and thus the production efficiency is extremely poor.
Further, with use of higher resolution of 0.07 μm or less, patterns are also coming thinner. In connection with such a situation, there is desired a resist material having still higher etching resistance.